The present invention relates to the finishing and cutting of paper and other graphic and photographic substrates, and in particular to an automatic device which allows, in a quick and simple manner, the cutting, possibly at right angles, of said substrates printed by digital rendering systems.
It is known that the photographic technique is undergoing a deep transformation and the present tendency is to use digital printing systems for all those jobs previously made with conventional optical systems.
The systems which are presently available have the feature of printing at the same speed on substrates of different size, usually on reels which can reach a width of about 140 cm. In order to increase the productive capacity, given the unlimited possibility of paging of said systems, multiple copies of smaller size, arranged mutually parallel and perpendicularly to the longitudinal axis of the reel, are printed through a single exposure on the largest size allowed.
The print in different sizes and at different positions makes the known cutting systems unusable. The cutting operation is then usually carried out with manual means (cutters, etc.) or semiautomatic means which require of the operator the optical/manual alignment on the cutting line of the gap between the prints. This implies the need for continuous attention with a possibility of error and a significant waste of time, this drawback being so serious because the amount of time spent by the operator(s) to treat the material is greater.
Therefore there is a clear necessity for devising systems which relieve the operator of the manual performing of this delicate operation, by making it automatic and thus allowing for a quick, simple and precise way of carrying it out.
Among the attempts of solution provided in the prior art, the U.S. Pat. No. 5,586,479 discloses a device for cutting images printed on substrates in sheets not parallel to the sides of the substrates. This prior patent deals with the problem of defining the cut along the edge of the print even when there are no evident optical contrast between the substrate and the image by creating, though suitable software, small back marks upstream from the copy. The optical sensors are provided at the side of the substrate and thus the latter must be guided and the sensors"" arrangement and position has to be changed at every change in the size, which is particularly disadvantageous when the substrate is made in single sheets.
Anyway, such an automatic cutting system was already used by the applicant since 1986 for paper reels and photocomposition film based on the optical reading of the edge and the creation of a mark. In order to prevent problems of reading errors and misinterpretation of the mark, also the parameter of its length to be measured for acceptance was used, in addition to other security means.
Also the U.S. Pat. No. 5,079,981 relates to an automatic cutting device, in particular for transparent substrates with automatic alignment of the blade on the substrate thanks to two sensors which detect at two different points the transparency/opacity threshold between substrate and image. The time lag between the two signals is converted by a processor into a number of pulses which are used to correct the cutting angle. However, this solution can only be used to trim and cut copies enclosed one by one into a transparent film, while it is clearly useless for separating copies within a larger size where the opacity is constant.
Therefore the object of the present invention is to provide an automatic cutting device, which possibly cuts at right angles, allowing to divide one by one the multiple copies in a quick and simple manner according to the positioning set by the system software during the printing step, without the drawbacks of prior art devices.
The main feature of the device according to the present invention is that it provides for complex linear optical marks being inserted between the copies or prints, where the cutting is required, which can be easily detected by continuous scanning so as to be cut or removed by means of a double cut parallel to the length of the mark. In this way, the cutting angle correction is carried out with respect to a mark and not to the edge of an opaque material laminated on a transparent material or of images printed not perpendicular to the substrate, which requires side guides. In fact, an important advantage of the present invention is that it can perform the cutting of substrates both in reels and in sheets, even without any guiding system.